1. Field of the Invention
The present invention generally relates to a magneto-optical recording apparatus. More particularly, the present invention is directed to the structure of the magnetic head portion of a magneto-optical recording apparatus.
2. Description of the Prior Art
As is well known in the art, the functions of a magneto-optical recording apparatus are to heat a portion of a magnetic recording medium by irradiating a laser beam onto the magnetic recording medium so as to reduce the coercive force of the irradiated medium portion, and to perform the recording operation under the above-described conditions. That is to say, the magneto-optical recording apparatus realizes perpendicular magnetic recording with a relatively small magnetic flux.
FIG. 25 schematically illustrates the prior art magneto-optical recording system. A magnetic recording medium 11 has a vertical (perpendicular) magnetizing film 13 on a light-transmitting substrate 12. A surface of the vertical magnetizing film 13 is covered with a protecting film 14. While a laser beam "L" focused by a light collecting lense 14 is projected onto the vertical magnetizing film 13, the film portion to which the laser beam is projected is subjected to a heat. A magnetic head 16 performs vertical (perpendicular) magnetic recording on the heated portion, of the vertical magnetizing film 13, and is constructed by winding a coil 18 around a bar-shaped magnetic core 17. The vertical magnetizing film 13 is vertically magnetized by flowing a recording current through the coil 18, so that the vertical, or perpendicular magnetic recording is carried out by the magnetic head 16.
In the conventional magneto-optical recording apparatus according to the above-described principle, theoretically, it is preferable that the strength of the recording field of the magnetic flux generated from the tip portion of the magnetic core 17 has its maximum value at the vertical magnetizing film 13. Since, however, the magnetic recording medium 11 is fabricated from, generally speaking, a soft material such as a synthetic resin, there is a limitation on the flatness of the magnetic recording medium. As a result, surface vibrations caused by rotation cannot be avoided. It is therefore required to introduce a predetermined spacing "S" between the magnetic recording medium 11 and magnetic head 16 so as to prevent the actual contact therebetween caused by these surface vibrations. Because, as previously stated, this spacing "S" is present and the edge of the magnetic core 17 has a flat shape as shown in FIG. 25, a large magnetic field is necessarily required to realize the vertical magnetization. In other words, the advantage of the magneto-optical recording apparatus where recording can be performed with a small magnetic field is substantially lost.
Taking account the above conventional art drawbacks, the Applicant has proposed in, for instance, Japanese patent application No. 62-30274 improvements in the tip shape of the magnetic head, whereby magnetic flux is concentrated onto the vertical magnetizing film 13 in order to increase the magnetic field efficiency. However, this solution has the following problem. That is, since the diameter of the core constituting the magnetic head cannot be made small, then the inductance of the magnetic circuit is large which is not suitable to produce a high frequency magnetic field.
Furthermore, the Applicant has proposed in Japanese patent application No. 62-223795 that a plurality of coils having cores of narrower diameters are employed for the magnetic head to concentrate the magnetic flux generated from the respective tip portions of these cores so that the inductance is small, and the strong magnetic field is applied to the magnetic recording medium.
Objects of the present invention are to improve the following with reference to the prior applications filed by the Applicant.
1) The structure of the magnetic head is simplified and readily machined.
2) The electromagnetic converting effect is increased.
3) A compact magnetic head is manufactured while maintaining magnetic recording efficiency.